/Engine/Source/Runtime/Engine/Classes/GameFramework/MovementComponent.h
Slide smoothly along a surface, and slide away from multiple impacts using TwoWallAdjust if necessary. Calls HandleImpact for each surface hit, if requested. UsesSafeMoveUpdatedComponent()for movement, andComputeSlideVector()to determine the slide direction.
The percentage of requested distance (Delta * Percent) actually applied (between 0 and 1). 0 if no movement occurred, non-zero if movement occurred.
virtual float SlideAlongSurface ( const FVector & Delta, float Time, const FVector & Normal, [FHitResult](API\Runtime\Engine\Engine\FHitResult) & Hit, bool bHandleImpact )